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Green roofs

12 July, 2011 | By Sandy Patience

Sika Sarnafil

[Sustainable products] Easy to install and delivering real benefits, green roofs are more popular than ever, says Sandy Patience

Cynics point to the proliferation of green roofs and claim that, like strapping wind turbines to a building, they are an easy route to green credibility. However, green roofs can deliver real environmental benefits.

Since entering the mainstream, recognition of the many benefits green roofs can bring has been reflected in the growth of policy, planning support, research and technological development.

London is at the forefront of policy, where green roof installation is encouraged through the London Plan. The Environment Agency also publishes an online toolkit to help developers and designers through the decision-making process.

Because of their low demand on structure, maintenance and budget, ‘extensive’ green roofs continue to be the most specified. More rapid installation with lower risk of failure is enabled through the development of pre-cultivated sedum blankets brought to site and laid upon single integrated filtration, drainage and protection layer systems.

Another development that offers rapid green roof installation is the grid module. Containing the entire planting and substrate within small plastic ‘baskets’ located together over the waterproofing layer, modular systems claim advantages of prefabrication and flexibility.

In recent years, the well-known ‘extensive’ and ‘intensive’ planting systems have been joined by a variation that recognises the importance of local habitats. A ‘biodiverse’ or ‘brown’ roof is a green roof designed specifically to encourage biodiversity through using local soil and spoil. Emphasis is on naturally occurring growth rather than planting imposed by the designer.

Designing a green roof involves the selection of a number of components that will include membrane protection, a drainage system, a growing medium as well as the planting. Products can be combined from a number of sources, but most roof membrane manufacturers offer, themselves or with horticultural suppliers, complete systems.

TRELLEBORG

Trelleborg

GreenGrid offers a modular design that contains all the separate layers that make up a traditional green roof in one unit. The modules arrive on site preplanted and ready for installation, lessening the risk of plant failure.

IKO

IKO

A form of extensive roof that makes use of recycled materials in the growing medium. This type of green roof is intended to create a natural wasteland and can be seeded initially with selected species to create some growth.

BAUDER

Bauder

A biodiversity roof that provides a natural living habitat to encourage a wider spread of birds, insects and plant species in the area. It generally seeks to replicate the ecological environment of the site upon which construction development is taking place.

SIKA SARNAFIL

Sika Sarnafil

Extensive systems are selfsustaining, naturalistic and low maintenance. Suitable for both flat and pitched-roof applications, they provide a raft of building performance benefits, reduce building impact and over time create a general habitat for a variety of flora and fauna.

LANGLEY

Langley

The low growth characteristics of sedums makes them particularly suitable for growing in the inhospitable conditions found on roofs. It is the very nature of the sedum plant that makes it perfect for survival in drought conditions.

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